This project describes the Core Facilities of the Data Coordinating Center for the study on Azithromycin in Control of Trachoma. The disciplines represented by this core facility include epidemiology, biostatistics, clinical trial expertise, and data management and systems analyses. The investigators have considerable experience in conducting data coordinating center activities for clinical trials, international epidemiologic studies and randomized community trials in trachoma, and the development of quality assurance techniques for field use in multiple international settings. The Data Coordinating Center will work with each principal investigator to coordinate the design, conduct and analyses of the four main projects: A clinical trial of Azithromycin in the treatment of trachoma, the study of re-emergent trachoma in villages following mass treatment, the genetic epidemiology of C. trachomatis infection in trachoma endemic areas, and immune responses to trachoma infection following treatment. The integration of this program project is reflected in the efficiency of a core facility for coordinating all data collection, management, and analyses.